Can I connect a 5w 5w solar panel directly into a 10k mAh portable battery bank safely via USB 2.0, or does it need some sort of protection in-between like a solar charge controller or a schottky diode?
Example of battery bank (except one with usb 2.0 input): https://www.anker.com/ca/products/a1229
Example of solar panel: https://www.aliexpress.com/item/1005006012344670.html
Are you going to wire the solar to a usb connector and plug it into the bank charging port? This is probably the safer way of approaching this.
Also, sometimes the quoted voltage is a “nominal working voltage” kind of deal. Grab a multimeter and see how many volts the solar cell puts out at noon without any load, it might be in the 8v range that could pose an overvoltage problem to your bank (that’s expecting 5v ) if it fills up completely.